Refrigerator and Solar advice for newbie

[cjweener1]

Bought the truck and now in the final stages of ordering a new Northstar Arrow U

I'd like to hear what folks prefer for refrigerators....2 way vs 12 volt compressor. I've read the pros and cons but still not sure which way to go. I'm concerned about the power requirement of the compressor fridge but really like it's performance/safety/ease of use vs. the propane. How much of a solar system do you need (rough estimate) to operate a 6 cu. ft. compressor fridge/freezer and basic electrical needs of camper...LED lights/electric jacks/pump/electronics incl. TV (NO A/C or Microwave).


We have room for 2 group 31 AGMS's for battery storage inside the camper. I can add the factory option of a Zamp 150 watt solar system but not sure how much room will be left over for an additional panel. We do have a Yamaha 2000 for back-up charging if need be. I know we could add our own solar system after purchase and just have them pre-wire it...but hubby is not too excited about this. He is a handy guy but is ready to retire and play

I'd like to get a feel for how much solar folks are installing on their roofs and panel size/configuration, etc. I've read Mello Mike's most excellent articles and am still not sure which way to go. Please share what you have done. I'm so grateful for this forum and all the help you have given us newbies!

[computerguy]

There is no simple answer. You need to do the math. It's known as an energy audit. Look up each device you would like to run. Then multiple that by t eh number of hours you want to run each device. Multiple it out then add up the sum for each and then you have the needed energy for a day.
For example I want to run a 2 amp 12v device for 4 hours a day.
12 x 2 = 12 x 4 = 96
96 amp hours would be needed
Ok, to your panels. You get about 5 hours of peak power from the sun. 96/5=19.2 amps per hour would be what you would need to put into your battery bank. Now, I am sure some will say well, this is not good because you need to consider how flooded lead acid batteries will not accept the full amount for the entire time. Yes, this is correct but I am trying hard to make this simple so the basics are understood. Back to the example, you need 19.2 amps at 14.4 volts or higher to replaced the needed energy. A 160w panel can produce 8 or so amps per hour in perfect conditions (77 Fahrenheit, no clouds, no shading etc). You can see 2 160w panels doesn't quite meed the demand. 3 panels does.
add up your demand and then you can determine the answer to your question.

[yorgor]

Forget 12 V, except for emergency. I have used propane for many years without any problems.

[twinboat]

Originally Posted by computerguy

There is no simple answer. You need to do the math. It's known as an energy audit. Look up each device you would like to run. Then multiple that by t eh number of hours you want to run each device. Multiple it out then add up the sum for each and then you have the needed energy for a day.
For example I want to run a 2 amp 12v device for 4 hours a day.
12 x 2 = 12 x 4 = 96
96 amp hours would be needed
Ok, to your panels. You get about 5 hours of peak power from the sun. 96/5=19.2 amps per hour would be what you would need to put into your battery bank. Now, I am sure some will say well, this is not good because you need to consider how flooded lead acid batteries will not accept the full amount for the entire time. Yes, this is correct but I am trying hard to make this simple so the basics are understood. Back to the example, you need 19.2 amps at 14.4 volts or higher to replaced the needed energy. A 160w panel can produce 8 or so amps per hour in perfect conditions (77 Fahrenheit, no clouds, no shading etc). You can see 2 160w panels doesn't quite meed the demand. 3 panels does.
add up your demand and then you can determine the answer to your question.

Maybe I'm missing something in your math.

2 amps for 4 hours is 8 AH.

[computerguy]

Dang. Musta been the new math. Sorry. I think I was converting/thinking along the line I was converting to AC
Apologies. I'll try and update it later. Off for a bike ride :(

[twinboat]

It was explained to me, back in 2012, when I built my system, that you take your solar watts ÷ by 13.5 ( charging volts ) × 5.5 hours of sun a day.

Example: 200 watts ÷ 13.5 = 14.8 AH.
14.8 AH × 5.5 hours of sun = 81 AH per day.

An example of energy use: I have a small apartment size 7.6 CF fridge that draws 8 amps @12 volts DC. It runs about 1/3 the time.

24 ÷ 3 = 8 hours total run time, at 8 amps = 64 AH per day.

You need an energy audit of all of your equipment used to design a sustainable system.

[cjweener1]

Thanks for the responses! I'm leaning propane....thanks yorgor! I think the 12 volt compressor would be nice but I'm getting a little overwhelmed with all the decisions on the rig and worried about the power drain of the 12volt.

I think I'll go factory 150 watt solar....2 31 AGM's, Yamaha 2000 (already have) for back-up and see what my power needs are. I'm going to learn by the school of hard knocks. Thanks everyone!

[vsheetz]

Having had both RR and electric/propane, we much prefer the RR. Add another pair of six volt batteries to handle it.

[baphenatem]

A pair of group 31 AGM's will give you about 100 Amp-hours of usable capacity (if they're inside and warm). Your largest electrical load will be the furnace blower in cold weather. The current draw depends on the furnace. I know from experience that between my furnace and CPAP machine, on a cold night they will use up about 50Ah, which is pretty much the max for my single group 31 deep cycle battery.

Looking on a couple of marine supplier sites, it appears that the average draw for a 12 volt compressor fridge is about 400Wh per day, or about 33 Ah. Add in a couple of other small loads and you're easily in the 100Ah range, but then again, your loads may be less. With 150W of solar, mounted flat, you may get an average charge rate of about 6-8 amps with a basic PWM charge controller, times 5 hours (if you're lucky), gives about 40Ah, max. This means that you'll be getting the generator out quite frequently.

While I wouldn't discourage you from having the factory installed solar charging system put on, as it will help to keep your batteries in good shape during storage periods, I would encourage you to consider all possible means to reduce your electrical usage if you want to boondock regularly. Those measures would be to go with the 2-way propane fridge, and if you can do it, a catalytic or radiant LP heater, among others.

Personally, I'm not a fan of the Zamp kits for truck campers. Because of the limited roof space for solar modules you really need to maximize the system output, and that means using a MPPT charge controller. Also, you really need to have a good battery monitor. I put a Midnight Solar KID charge controller in mine, primarily because it can do the charging and monitoring in one unit, when paired with their WhizBang interface unit. The MPPT also enables you to somewhat oversize the array (if you have the space) which can help to get the charging done sooner. You may be able to fit about 400-500W of modules on the roof, which would make for a mighty fine setup with a pair of 31's and a 30 Amp MPPT charge controller.

[cjweener1]

Wow, great advice everyone! baphenatem...you have given me much to think about and your examples of realistic energy demands has been very helpful in my decision making process. We are going to get very creative at using less! Thanks to you all!!!

I'm going 2 way Dometic 6 cf reefer...(standard on Northstar). I also plan on configuring my trucks dual alternators to more efficiently recharge my batteries (large gauge wire, solenoid and fuses to protect everything, etc.) and try to learn more about solar systems and how I might be able to improve on that...with some flexibility to add on if need be.


Thanks everyone!!!

[cjweener1]

baphenatem...I checked out your recommendations on the Midnight Solar KID charge controller and monitor with the Whizbang...pretty slick! Not too bad of prices either....$280 ish plus around $50 for the Whizbang. (It was much higher on Amazon).
If you were in my TC shoes...and you don't mind me asking....how would you set up a system like this? What PV panels do you like...etc. You've got me thinking.....

[baphenatem]

Originally Posted by cjweener1

baphenatem...I checked out your recommendations on the Midnight Solar KID charge controller and monitor with the Whizbang...pretty slick! Not too bad of prices either....$280 ish plus around $50 for the Whizbang. (It was much higher on Amazon).
If you were in my TC shoes...and you don't mind me asking....how would you set up a system like this? What PV panels do you like...etc. You've got me thinking.....

There is no single clear answer on this. The biggest issue on truck campers is finding the room for the modules without having shading issues from vents and the AC unit. With a MPPT charge controller you can go with 36, 60, or 72 cell modules as long as you use the same type for parallel connected modules. The first thing that I look for is whether the module is listed by a nationally recognized test laboratory, such as UL, ETL or CSA. Next, I consider what will fit and whether I'm willing to spend extra for either high wattage 36 cell, or high efficiency modules. If so, what is the cost for shipping, as truck freight may exceed the cost of the modules.

Modules have largely become an industrial commodity and the performance spec on most of them are similar with about 15% efficiency under ideal conditions. Some of the premium units like, LG, Sunpower, and Panasonic are in the 20% range, but generally are high wattage modules that don't fit well on TC's.

Most folks seem to be going with Renogy 100's, but the HQST-100D is identical and about $20 per module less expensive. There is also a 150W version of both of them, but the unusual shape and size doesn't lend itself to TC's, (unless it does for your application). Both are listed (monocrystalline only) and available from Amazon. If you go with these I would try to go with two series connected pairs, for a total of 400W. This strikes a balance between wire size and shading resistance. Kyocera 150's are usually on my list, but they are getting harder to find and cost twice as much per watt as their "Brand X" counterparts.

[vsheetz]

I have 15 of the Renogy 100 panels. Configured in three strings. They make a narrower/longer and a wider/shorter version. Mine are mostly the narrower/longer so as to minimize shading from other roof mounted equipment. Mine are mounted flat using the Renogy aluminum mount brackets. You can order directly from Renogy or they sell on Amazon.

I also have Midnite Solar controller (Classic 150) and Midnite​ Solar combiner box with circuit breakers. Good support is available for Midnite Solar.

[baphenatem]

One other safety feature on certain Midnite Solar controllers, and the Magnum PT-100 charge controller, is the arc fault protection, which is required by the electrical code when the PV voltage is 80 volts or higher. There are a couple of YouTube videos showing how this works and the difference is astounding.